Hydraulic fracturing pump system

ABSTRACT

A system for fracturing a subsurface formation may comprise a transport unit with hydraulic legs, an electric motor mounted on the transport unit, a fracking pump mounted on the transport unit and configured to be powered by the electric motor, and an oil tank mounted on the transport unit such that the motor and the fracking pump are above the oil tank. The oil tank may have a first tank height under the pump and a second tank height under the motor and the first tank height may be greater than the second tank height. The oil tank, motor support beam, and pump support beam may form a single structural unit. The system may also include an oil pump for pumping lubricating oil through the fracking pump, an electric motor configured to drive the oil pump, a variable frequency drive configured to control the electric motor.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a nonprovisional application which claims priority from U.S. provisional application No. 62/833,385, filed Apr. 12, 2019, which is incorporated by reference herein in its entirety.

Technical Field/Field of the Disclosure

The present disclosure relates to apparatus and methods for use in hydraulically fracturing subsurface formations.

BACKGROUND OF THE DISCLOSURE

Hydraulic fracturing may be used to increase hydrocarbon production from some subsurface formations. Hydraulic fracturing entails injecting fluid into a wellbore at a pressure sufficient to cause fissures in the formation surrounding the wellbore. The injected fluid may be a slurry or mixture containing any of a variety of water-, oil-, or gas-based fluids and a proppant and/or other desired additives.

In some instances, the fracturing fluid is pressurized at the surface by high-pressure pumps powered by diesel engines. In other instances, electric motors controlled by variable frequency drives are used place of the diesel engines and associated equipment. The use of electric motors greatly reduces the noise, emissions, and vibrations generated by the equipment during operation, as well as its size footprint.

Regardless of whether diesel or electric power is used to produce the pressures required for hydraulic fracturing, the pumps and associated engines tend to be bulky and heavy. In addition, a hydraulic fracturing system may include one or more of: data storage equipment, mixers, hydrators, chemical additive units, pumps, sand equipment, and the like. Thus, hydraulic fracturing equipment may be transported to hydraulic fracturing sites using heavy duty trailers, skids, or trucks capable of transporting heavy equipment.

SUMMARY

In some embodiments, a system for fracturing a subsurface formation, may comprise a transport unit, an electric motor mounted on the transport unit, a fracking pump mounted on the transport unit and configured to be powered by the electric motor, and an oil tank mounted on the transport unit such that the motor and the pump are above the oil tank. The oil tank may have a first tank height under the pump and a second tank height under the motor and wherein the first tank height is greater than the second tank height. The system may further include at least one beam supporting the motor and at least one beam supporting the pump, and the oil tank may be formed integrally with the beams. The oil tank may be permanently secured to the beams.

In some embodiments, a system for fracturing a subsurface formation, may comprise a transport unit including a frame, an electric motor mounted on the transport unit, a fracking pump mounted on the transport unit and configured to be powered by the electric motor, and an oil tank mounted on the transport unit such that the motor and the fracking pump are above the oil tank. The tank may include a tank floor and the system may further include at least one motor support beam mounted on the frame and supporting the motor, the motor support beam including a motor mounting surface that engages the frame and a motor support surface that engages the motor, and at least one pump support beam mounted on the frame and supporting the fracking pump, each pump support beam including a pump mounting surface that engages the frame and a pump support surface that engages the fracking pump. The motor mounting surface and the pump mounting surface may define a mounting plane P_(M) and the tank floor may lie below the mounting plane P_(M).

The at least one motor support beam may have an upper surface that defines a motor support plane P_(MS), the at least one pump support beam may have an upper surface that defines a pump support plane P_(PS), and the pump support plane P_(PS) may be above the motor support plane P_(MS) such that the bottom of the fracking pump is higher than the bottom of the motor. The oil tank may be formed integrally with the beams or permanently secured to the beams.

In still other embodiments, a system for fracturing a subsurface formation may comprise a transport unit including a frame, an electric motor mounted on the transport unit, a fracking pump mounted on the transport unit and configured to be powered by the electric motor, and an oil tank mounted on the transport unit such that the motor and the fracking pump are above the oil tank. The tank may include a tank floor and the system may further include at least one motor support beam mounted on the frame and supporting the motor and at least one pump support beam mounted on the frame and supporting the fracking pump. The oil tank, the motor support beam, and the pump support beam may be rigidly mechanically connected so as to form a single structural unit. The at least one motor support beam may include a motor mounting surface that engages the frame and a motor support surface that engages the motor and the at least one pump support beam may include a pump mounting surface that engages the frame and a pump support surface that engages the fracking pump. The motor mounting surface and the pump mounting surface may define a mounting plane P_(M) and the tank floor may lie below the mounting plane P_(M). The system may include multiple motors and pumps, and each pump may be configured to be powered by an associated motor and each pump is associated with a fluid tank that extends under the pump and its associated motor. Alternatively, the system may include multiple motors and pumps, wherein each pump is configured to be powered by an associated motor and a single fluid tank provides fluid to all of the pumps.

In still other embodiments, a system for lubricating hydraulic fracturing equipment may comprise an oil pump for pumping lubricating oil, an electric motor configured to drive the oil pump, a variable frequency drive configured to control the electric motor, an oil tank, and a lubricating circuit in fluid communication with the oil pump and the oil tank. The lubricating circuit may pass through the hydraulic fracturing equipment. The variable frequency drive may vary the oil pump speed based on an input comprising at least one of oil pressure and oil temperature. The system may further include at least one of a filter, a thermostatic valve, an oil cooler, a check valve, a pressure relief valve. The thermostatic valve may control a flow of oil through the oil cooler based on oil temperature. The oil tank may be positioned beneath the hydraulic fracturing equipment. The hydraulic fracturing equipment may further include a fracking pump.

In still other embodiments, a transportable system for fracturing a subsurface formation may comprise a transport unit including wheels and a frame, a hydraulic fracturing pump unit mounted on the frame, and at least one pair of hydraulic landing legs positioned on opposite sides of the transport unit and adapted to, in conjunction with the wheels, support the transport unit. The hydraulic landing legs may be adjustable using hydraulic pressure. The system may further include a DC-powered hydraulic fluid pump in fluid communication with the hydraulic landing legs, a valve system with a switch for controlling each hydraulic landing leg, an integrated safety valve to prevent hydraulic collapse, a DC battery to provide power to the hydraulic fluid pump and valve system, and/or an in-transit battery charging system or a standby AC-powered battery charging system.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is best understood from the following detailed description when read with the accompanying figures. It is emphasized that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a side elevation of a transportable hydraulic fracturing system in accordance with one embodiment.

FIGS. 2-4 are top, side and end views, respectively, of a tank and beam combination for use in a transportable hydraulic fracturing system.

FIG. 5 is a schematic illustration of a lubricating system for use with hydraulic fracturing equipment.

FIG. 6 is a schematic illustration of a hydraulic landing leg system for use with hydraulic fracturing equipment.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides many different embodiments, or examples, for implementing different features of various embodiments. Specific examples of components and arrangements are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Referring initially to FIG. 1, transportable hydraulic fracturing system 10 in accordance with some embodiments may comprise several components including but not limited to: transport unit 20, pump unit 30, tank and beam assembly 40, variable frequency drive (VFD) house 60, condensers 70 and control valve system 100. Transport unit 20 may comprise a trailer configured for use with a tractor. Transport unit 20 may include wheels 21 and frame 22 on which some or all of the afore-mentioned components may be mounted. Transport unit 20 may further include at least one pair of hydraulic landing legs 24.

As disclosed in greater detail below, it may be desirable to provide pressurized oil lubrication to some of the components of pump unit 30. Lubricating oil that has passed through the pump unit may be collected and recycled. The collected oil may be stored, along with supplemental oil if desired, in a dedicated oil tank. As further set out below, the dedicated oil tank may be configured to provide mechanical and structural support to pump unit 30.

In some instances, it may be desirable to leave trailer-mounted hydraulic fracturing components attached to the tractor throughout operations, i.e. to conduct fracturing operations without unloading the fracturing equipment from the transport unit on which it was transported to the wellsite. When the pump is diesel-driven, a tractor may be left connected to the transport unit so that the engine of the tractor may be used to start the high-pressure pump engine. In contrast, electric high-pressure pumps do not need a transport tractor in order to start or operate. Thus, in hydraulic fracturing operations in which electric high-pressure pumps are used, the trailer can be dropped and the tractor removed, thereby allowing more efficient transport fleet operations.

When a trailer is dropped, one or more landing legs are extended so that the weight of the trailer is distributed between the trailer wheels, which may be at or near the rear of the trailer, and the landing legs, which may be at or near the front of the trailer. The tractor can then be decoupled from the trailer. Because the fracturing equipment components can be very heavy, it may be difficult to operate a manual front landing leg. In particular, once the tractor has been decoupled, manual adjustment of the landing legs may be difficult or risky. In addition, in some instances, manual landing legs do not facilitate the adjustment of each leg height independently, with the result that the front of the trailer cannot be leveled side-to-side.

Therefore, in some embodiments, a leg hydraulic system 90 may be associated with each landing leg. Referring briefly to FIG. 6, an exemplary leg hydraulic system may comprise one or more hydraulic legs 91, DC-powered hydraulic pump 92, control valve system 100 for controlling the flow of hydraulic fluid from the pump 92 to each leg 91 and having optional hand switch operators for each leg, motor 93 for driving pump 92, hydraulic fluid reservoir 95 in fluid communication with hydraulic pump 92, integrated safety valve 94 to prevent hydraulic collapse, DC battery 96 to provide power to the hydraulic pump and valve system, control system 97, and, optionally, in-transit battery charging system 98 and/or standby AC-powered battery charging system 99. The use of hydraulically operated front landing legs improves ease of operation, safety and allows for independent side to side leveling.

Referring again to FIG. 1, in some embodiments, pump unit 30 may include an electric motor 32, one or motor cooler blowers 34, and at least one high-pressure fracking pump 36 that increases the pressure of the fracking fluid to a desired level. A mechanical coupling 35 may couple the output of motor 32 to the input of fracking pump 36. In some embodiments, motor 32 and fracking pump 36 are mechanically connected via coupling 35 before the equipment is transported to the wellsite; in some such embodiments, coupling 35 may remain coupled to both motor 32 and fracking pump 36 throughout operations. During operations, fracking pump 36 receives low-pressure fracking fluid and outputs the fracking fluid at pressures suitable for fracturing the desired subsurface formation(s), which may be on the order of 50 MPa or more.

Referring now to FIGS. 2-4, tank and beam assembly 40 may include a tank and a plurality of beams adjacent to or surrounding the tank. An exemplary tank and beam assembly may include oil tank 42, at least one motor support beam 52, and at least one pump support beam 56, discussed in more detail below. In some embodiments, oil tank 42 may include various openings, including but not limited to: tank outlet 43, clean-out 44, fill opening 45, spare opening 46, one or more return openings 47, sight eye 48, and one or more auxiliary ports 49 (FIG. 4). Auxiliary ports 49 may be used for any additional equipment, including but not limited to draining or flushing equipment or heaters. During hydraulic fracturing operations, oil may be pumped from tank outlet 43 into the housing or frame case of fracking pump 36, where it lubricates and may cool the components of fracking pump 36.

Oil tank 42 may have an upper surface 51 and a tank floor 57. Oil tank 42 may comprise a relatively shallow section 53 and a relatively deep section 55 (shown in phantom in FIG. 4). Between shallow section 53 and deep section 55, upper surface 51 may include transition 54 (FIG. 3). In some embodiments, shallow section 53 may be narrower than deep section 55, as illustrated in FIGS. 2 and 4.

In some embodiments, one or more motor support beams 52 and pump support beams 56 may each be mounted on frame 22 of transport unit 20 such that the longitudinal axis of each beam is transverse to the longitudinal axis of the transport unit 20. Motor support beams 52 and pump support beams 56 may each have a mounting surface, 52 a, 56 a, respectively. Mounting surfaces 52 a, 56 a may rest on frame 22 of transport unit 20. Motor support beams may each also have motor support surface 52 b on which motor 32 may be mounted. Similarly, pump support beams may each have a pump support surface 56 b on which pump 36 may be mounted. As illustrated in FIG. 3, motor support beams 52 and pump support beams 56 may be positioned and configured such that the mounting surfaces 52 a, 56 a define a mounting plane P_(M), motor support surfaces 52 b define a motor support plane P_(MS), and pump support surfaces 56 b define pump support plane P_(PS). Pump support plane P_(PS) may be above motor support plane P_(MS) such that the bottom of fracking pump 36 is supported farther above the ground than the bottom of motor 32.

In some embodiments, the shallow section 53 of oil tank 42 extends parallel to the longitudinal axis of transport unit 20 through the plane of each motor support beam 52. Likewise, the deep section 55 of oil tank 42 extends parallel to the longitudinal axis of transport unit 20 through the plane of each pump support beam 56. The upper surface 51 of oil tank 42 may be configured such that the upper surface of shallow section 53 lies below motor support plane P_(MS) and the upper surface of deep section 55 lies below pump support plane P_(PS). Some or all of tank floor 57 may lie below mounting plane P_(M), in which case the volume of oil tank 42 that lies below mounting plane P_(M) may be referred to an oil sump. Oil suction opening 43 may be configured to take oil from the oil sump.

In some embodiments, oil tank 42 is constructed to be functionally integral with motor support beams 52 and pump support beams 56, by which is meant that oil tank 42 may be formed integrally with beams 52, 56 or secured thereto by welds, bolts, or the like. In some embodiments, oil tank 42 may be secured permanently to beams 52, 56 and/or to frame 22 and not separated therefrom during transport and operation of the system. Oil tank 42 may itself function as a structural component in conjunction with beams 52, 56. Together oil tank 42 and beams 52, 56 form a base assembly that is stronger and more resistant to deformation than either component would be separately.

For example, in embodiments in which tank floor 57 lies below mounting plane P_(M) as illustrated in FIG. 3, the total height of the tank and beam assembly 40 is greater than the distance between mounting plane P_(M) and pump support plane P_(PS). This increases the flexural strength of the tank and beam assembly and results in a stiffer assembly. Likewise, the interconnection between oil tank 42 and multiple beams 52, 56 results in a unitary assembly that is better able to resist torque and other forces that might otherwise cause relative displacement of the supported components, i.e. motor 32 and fracking pump 36. Because motor 32 and fracking pump 36 may each weigh 16,000 to 20,000 lbs. (7,000 to 10,000 kg) it may be advantageous to support upwards of 40,000 lbs. (20,000 kg) without allowing deflection in any direction.

Thus, an advantage of the tank assembly disclosed herein is that it provides a rigid frame that is well-adapted to maintain the relative positions and coupling between the high pressure slurry pump and its motor. Minimizing movement within the coupling ensures proper shaft alignment and prevents premature wear and failure of the pump and/or motor. A rigid frame also ensures that pump/motor alignment is maintained during transport of the unit from one wellsite to another.

As illustrated, tank and beam assembly 40 may be mounted on transport unit 20. The ability to locate the tank on the trailer typically results in the selection of an oil tank with limited capacity because of the limited space to locate the tank. An integrated tank and base in accordance with the concepts disclosed herein allows for increased oil capacity, better trailer stability (because it is not located off the center line of the trailer), better gravity oil return flow from the high-pressure pump to the tank because the tank is directly below the high-pressure pump and closely coupled thereto, and better flow to the oil pump because most of the volume of the tank is above the inlet of the pump.

Further, it may be desirable to not remove the coupling during transport because realignment of the pump/motor unit may be time-consuming. Thus, if the pump and motor can remain coupled during transport, substantial time-savings may be realized. The base assembly disclosed herein is sufficiently rigid to hold the equipment in alignment and prevent any relative movement that would damage the pump/motor coupling. A hydraulic fracturing system 10 as disclosed herein can be readily transported to a well site on a transport unit 20, which may comprise a trailer or other platform or frame equipped with wheels or tracks.

In some embodiments, oil tank 42 holds lubricating oil for fracking pump 36. Lubricating oil from oil tank 42 may be pumped by a VFD-driven lube pump system. FIG. 5 is a schematic illustration of an embodiment of a lubricating system for lubricating a fracking pump in accordance with concepts disclosed herein.

In some embodiments, a VFD-driven lube pump system includes software control system that controls VFD 72, which in turn controls motor 74, which may be an electric motor. Motor 74 drives oil pump 76, which pumps lubricating oil through a desired lubricating circuit 80. Motor 74 and oil pump 76 may each be mounted in any suitable location on transport unit 20, including for example, on the lower outside of the trailer frame ahead of the tires and wheels. As shown in the exemplary embodiment in FIG. 5, lubricating circuit 80 passes through fracking pump 36 and may further include any or all of: filter 82, thermostatic valve 83, cooler 84, check valve 85, pressure relief valve 86, and storage tank 88. Storage tank 88 may optionally comprise tank and beam assembly 40. Oil pump 76 takes lubricating oil from a storage tank 88, pumps the lubricating oil through a desired lubricating circuit 80, and returns the lubricating oil to the storage tank 88. If present, filter 82 may serve to remove debris from the lubricating oil. If present, thermostatic valve 83 and cooler 84 cooperate to allow the lubricating oil to shed heat if the temperature of the lubricating oil exceeds a predetermined value. If the temperature of the lubricating oil is below a predetermined value, cooler 84 may be bypassed. Thermostatic valve 83 may sense the oil temperature, or the oil temperature may be sensed elsewhere and provided as an input to thermostatic valve 83. Cooler 84 may be a radiator or any other heat-removal device. If present, check valve 85 prevents backflow through the lubricating circuit 80. If present, pressure relief valve 86 enables venting if pressure in the lubricating circuit 80 exceeds a predetermined value.

Because the high-pressure fracking pump 36 requires a continuous supply of pressurized lubricating oil while fracking pump 36 is running, inconsistent delivery of lubricating oil to fracking pump 36 may affect fracking operations. The lubricating oil pressure may vary, based on oil temperature, high-pressure pump speed and other external factors. A lubricating oil pressure that is too high or too low can result in premature wear and failure of the high-pressure fracking pump. One way to control the lubricating oil system pressure is by controlling the speed of oil pump 76. In instances where the fracking pump is driven by a diesel engine, an oil pump may be driven by a power take-off on the same diesel engine and the lube oil system pressure may be controlled by varying the engine speed of the diesel engine. By contrast, in the present VFD-driven lube pump system, the lube oil system pressure can be controlled by the use of a variable frequency electric drive to vary the speed of the electric motor, which in turn can vary the speed of oil pump 76. The VFD can be controlled by software that varies the lube oil pump speed based on inputs including but not limited to oil pressure and temperature. A VFD-driven lube pump system ensures that the high-pressure fracking pump 36 always has an appropriate supply of pressurized lube oil.

Those skilled in the art will appreciate that numerous changes and modifications can be made to the embodiments of the present disclosure and that such changes and modifications can be made without departing from the spirit of said disclosure. It is, therefore, intended that the appended claims cover all such equivalent variations as fall within the true spirit and scope of said disclosure. 

What is claimed is:
 1. A system for fracturing a subsurface formation, comprising: a transport unit; an electric motor mounted on the transport unit; a fracking pump mounted on the transport unit and configured to be powered by the electric motor; and an oil tank mounted on the transport unit such that the motor and the pump are above the oil tank, the oil tank including a tank floor; wherein the oil tank has a first tank height under the pump and a second tank height under the motor and wherein the first tank height is greater than the second tank height.
 2. The system according to claim 1, further including at least one motor support beam supporting the motor and at least one pump support beam supporting the pump, and wherein the oil tank is formed integrally with or permanently secured to the motor support beam and the pump support beam.
 3. The system according to claim 2 wherein the transport unit includes a frame, wherein the motor support beam includes a motor mounting surface that engages the frame and a motor support surface that engages the motor, wherein each pump support beam includes a pump mounting surface that engages the frame and a pump support surface that engages the fracking pump, wherein the motor mounting surface and the pump mounting surface define a mounting plane P_(M); and wherein the tank floor lies below the mounting plane P_(M).
 4. The system according to claim 3 wherein the at least one motor support beam has an upper surface that defines a motor support plane P_(MS), wherein the at least one pump support beam has an upper surface that defines a pump support plane P_(PS), and wherein the pump support plane P_(PS) is above motor support plane P_(MS) such that the bottom of the fracking pump is higher than the bottom of the motor.
 5. The system according to claim 4 wherein the oil tank, the motor support beam, and the pump support beam are rigidly mechanically connected so as to form a single structural unit.
 6. The system according to claim 5 wherein the oil tank is formed integrally with the beams.
 7. The system according to claim 5 wherein the oil tank is permanently secured to the beams.
 8. The system of claim 5 wherein the system includes multiple motors and pumps, wherein each pump is configured to be powered by an associated motor and each pump is associated with a fluid tank that extends under the pump and its associated motor.
 9. The system of claim 5 wherein the system includes multiple motors and pumps, wherein each pump is configured to be powered by an associated motor and a single fluid tank provides fluid to all of the pumps.
 10. A system for lubricating hydraulic fracturing equipment, comprising: an oil pump for pumping lubricating oil; an electric motor configured to drive the oil pump; a variable frequency drive configured to control the electric motor; an oil tank; and a lubricating circuit in fluid communication with the oil pump and the oil tank, the lubricating circuit passing through the hydraulic fracturing equipment.
 11. The system according to claim 10, further including at least one motor support beam supporting the motor and at least one pump support beam supporting the pump, and wherein the oil tank is formed integrally with or permanently secured to the motor support beam and the pump support beam.
 12. The system of claim 11 wherein the variable frequency drive varies the oil pump speed based on an input comprising at least one of oil pressure and oil temperature.
 13. The system of claim 11, further including at least one of a filter, a thermostatic valve, an oil cooler, a check valve, or a pressure relief valve.
 14. The system of claim 11 wherein the hydraulic fracturing equipment includes a fracking pump and wherein the oil tank is positioned beneath the hydraulic fracturing equipment.
 15. A transportable system for fracturing a subsurface formation, comprising: a transport unit including wheels and a frame; a hydraulic fracturing pump unit mounted on the frame; and at least one pair of hydraulic landing legs positioned on opposite sides of the transport unit and adapted to, in conjunction with the wheels, support the transport unit.
 16. The system of claim 15 wherein the hydraulic landing legs are adjustable using hydraulic pressure.
 17. The system of claim 16, further including a DC-powered hydraulic fluid pump in fluid communication with the hydraulic landing legs.
 18. The system of claim 17 wherein the hydraulic landing legs are independently adjustable, further including a valve system with a switch for controlling each hydraulic landing leg.
 19. The system of claim 18, further including an integrated safety valve to prevent hydraulic collapse.
 20. The system of claim 18, further including a DC battery to provide power to the hydraulic fluid pump and valve system.
 21. The system of claim 21, further including an in-transit battery charging system or a standby AC-powered battery charging system. 